UMTRI-2012-12
MAY 2012
CARBON CAPTURE IN VEHICLES:
A REVIEW OF GENERAL SUPPORT,
AVAILABLE MECHANISMS, AND
CONSUMER-ACCEPTANCE ISSUES
JOHN M. SULLIVAN
MICHAEL SIVAK
CARBON CAPTURE IN VEHICLES:
A REVIEW OF GENERAL SUPPORT, AVAILABLE MECHANISMS, AND
CONSUMER-ACCEPTANCE ISSUES
John M. Sullivan
Michael Sivak
The University of Michigan
Transportation Research Institute
Ann Arbor, Michigan 48109-2150
U.S.A.
Report No. UMTRI-2012-12
May 2012
1. Report No.
UMTRI-2012-12
Technical Report Documentation Page
2. Government Accession No.
3. Recipientʼs Catalog No.
4. Title and Subtitle
Carbon Capture in Vehicles: A Review of General Support,
Available Mechanisms, and Consumer Acceptance Issues
5. Report Date
May 2012
6. Performing Organization Code
383818
7. Author(s)
8. Performing Organization Report No.
9. Performing Organization Name and Address
10. Work Unit no. (TRAIS)
John M. Sullivan and Michael Sivak
UMTRI-2012-12
The University of Michigan
Transportation Research Institute
2901 Baxter Road
Ann Arbor, MI 48109-2150 U.S.A
11. Contracts or Grant No.
12. Sponsoring Agency Name and Address
13. Type of Report and Period Covered
The University of Michigan
Sustainable Worldwide Transportation
14. Sponsoring Agency Code
15. Supplementary Notes
The current members of Sustainable Worldwide Transportation include Autoliv Electronics,
China FAW Group, General Motors, Honda R&D America, Meritor WABCO, Michelin
Americas Research, Nissan Technical Center North America, Renault, Saudi Aramco, and
Toyota Motor Engineering and Manufacturing North America. Information about Sustainable
Worldwide Transportation is available at: http://www.umich.edu/~umtriswt.
16. Abstract
This survey of the feasibility of introducing carbon capture and storage (CCS) into light vehicles
started by reviewing the level of international support for CCS in general. While there have been
encouraging signs that CCS is gaining acceptance as a means to reduce carbon emissions, the overall
outlook looks somewhat mixed. Recent developments in the US, the UK, Germany, India, and China
are discussed to obtain an indication of how likely it is that CCS technologies will gain acceptance
in each respective country.
Fossil fuels continue to be a versatile means of energy storage, especially compared with
many low-emissions alternatives. This is noted because, apart from reduced fuel consumption,
CCS technology is key to reducing CO2 emissions produced by the use of fossil fuels in
transportation.
Primary focus in this review was placed on post-combustion-capture technologies because
these mechanisms are most easily adapted for use with the existing fleet of internal combustion
engines. Three post-combustion-capture mechanisms were described: absorption, membrane
separation, and adsorption.
Considerations about the consumer’s operational costs were discussed, including storage
management of captured CO2, additional energy costs to support separation and storage,
discharge procedures, and vehicle maintenance costs. Models of consumer inclination to adopt
new technologies were also reviewed. An important component of a consumer’s motivation to
adopt eco-friendly transport is perceived financial benefit. This suggests that incentives beyond
reduced emissions may be required to motivate consumer adoption of vehicle-based CCS because
the link between emissions and fuel consumption may change.
17. Key Words
18. Distribution Statement
Carbon capture, alternative fuels, consumer motivation, Unlimited
on board carbon capture
19. Security Classification (of this report)
None
20. Security Classification (of this page)
None
i
21. No. of Pages
22. Price
Acknowledgments
This research was supported by Sustainable Worldwide Transportation
(http://www.umich.edu/~umtriswt). The current members of Sustainable Worldwide
Transportation include Autoliv Electronics, China FAW Group, General Motors, Honda
R&D America, Meritor WABCO, Michelin Americas Research, Nissan Technical Center
North America, Renault, Saudi Aramco, and Toyota Motor Engineering and
Manufacturing North America.
ii
Contents
Acknowledgments............................................................................................................... ii Introduction ..........................................................................................................................1 General Overview of Carbon Capture and Storage .............................................................2 Level of support .............................................................................................................2 United Kingdom.............................................................................................................5 Germany.........................................................................................................................5 United States ..................................................................................................................5 India ...............................................................................................................................6 China ..............................................................................................................................7 Recent developments .....................................................................................................8 Conclusion .....................................................................................................................8 Carbon-Collection Processes in Vehicles ..........................................................................10 Why is fossil fuel combustion an attractive option? ....................................................10 Comparison of energy sources .....................................................................................11 Plausible in-vehicle carbon-capture mechanisms ........................................................18 Transport to long-term sequestration areas ..................................................................21 Considerations about the Operational Costs of Carbon Capture .......................................23 Amount of CO2 recovered ...........................................................................................23 Parasitic load of the in-vehicle capture process ...........................................................24 Discharge procedures for carbon capture ....................................................................25 Location of carbon-collection facilities .......................................................................26 Additional maintenance costs ......................................................................................27 Consumer Purchase Motivations .......................................................................................28 Conclusions ........................................................................................................................30 References ..........................................................................................................................32 iii
Introduction
In 2009, transportation in the United States was responsible for emitting
approximately 1,719.7 million metric tons of carbon dioxide into the atmosphere from
fossil-fuel combustion (United States Environmental Protection Agency, 2011b); in the
United States, the transportation sector is responsible for about 27% of all the greenhouse
gas emitted in the U.S. (United States Environmental Protection Agency, 2011b). Not
surprisingly, in the U.S., the transportation sector is responsible for proportionally more
emissions than the worldwide estimate of about 23% (International Energy Agency,
2011), although many developing nations such as China and India are quickly catching
up.
Combustion of one gallon of gasoline produces 8.9 kg of CO2 (United States
Environmental Protection Agency, 2011a). Over a year, the typical passenger vehicle
(assuming 21 miles per gallon, and 12,000 annual miles) generates 5.1 metric tons of
CO2.
Clearly, any effort to reduce such emissions will help address the growing
accumulation of greenhouse gases in the atmosphere.
Several strategies have been used to attack the problem of transportation
emissions, either by reducing or avoid the burning of fossil fuel. These include the
design of more fuel-efficient internal-combustion engines (ICE), use of alternative fuels
(e.g., biofuels, hydrogen, natural gas), and the development of alternative propulsion
systems based on electrical power, including hybrid-electric vehicles (HEV), plug-in
hybrids (PHEV), electric vehicles (EV), and hydrogen-based fuel-cell vehicles (FCV).
This report examines the broad feasibility of an alternate emissions-reduction strategy, in
which carbon capture and storage (CCS) methods are introduced into ICE passenger
vehicles. The main focus of the report is to highlight issues that are likely to be relevant
to consumers of passenger vehicles, without directly addressing issues of technical
feasibility. This includes a review of the current worldwide acceptance of carbon storage
methods, an exploration of the consumer’s perspective with regard to the likely
operational demands (e.g., maintenance, fueling), and of issues likely to drive consumer
preference for this technology.
1
General Overview of Carbon Capture and Storage
There is general acknowledgment that fossil fuels will continue to serve as a lowcost energy resource for the foreseeable future and that, if the target global concentration
of greenhouse gases set forth by the United Nations Intergovernmental Panel on Climate
Change (IPCC) are to be met, some form of CCS will be required (Global CCS Institute,
2011). At this point in its development, an important step is to demonstrate the feasibility
of the entire CCS processing chain, beginning with capture at the combustion site,
followed by compression, transportation, and injection into a permanent storage site. To
address this need, several world governments have launched CCS projects in a variety of
locales. The relative success of these projects may provide an early indication of how
quickly development is likely to produce a mature and workable solution, leading to the
development of an infrastructure to support distributed carbon capture.
If it is initially supposed that carbon dioxide capture is feasible in light vehicles,
there remains the issue of where the collected carbon dioxide will eventually be stored.
Currently, carbon capture and storage methods are in a relatively early stage of proving
feasibility through a series of demonstration projects. Unless these projects persuasively
demonstrate that carbon dioxide can be stored safely and with long-term stability,
development of the necessary infrastructure to transport carbon dioxide cheaply and
efficiently to its final resting place may languish. Besides the need to demonstrate
technical feasibility, commercial investment in CCS also requires legal and regulatory
policies to establish clear guidelines governing aspects of the transport and storage of
CO2—for example, regulations would be needed to establish legal responsibilities related
to transport (e.g., through CO2 pipelines), injection sites, and geological monitoring. In
the absence of such regulation, commercial investment would be at risk.
Level of support
Because CCS technology is thought by some to be a relaxing of the resolve to
develop renewable energy resources, in some environmental advocacy circles it is not
well supported. For example, Greenpeace has actively campaigned against CCS, labeling
underground storage of carbon dioxide “unproven” (Greenpeace, 2007), and a
2
“dangerous gamble” (Greenpeace, 2008). Similarly, projects involving CCS technology
were not initially authorized under the Kyoto Protocol’s Clean Development Mechanism
(CDM). Under CDM, developed countries could be credited with Certified Emission
Reductions (CERs) by investing in projects hosted by developing countries that
contributed to sustainable development.
CERs could then be applied toward the
investing (developed) country’s carbon-emissions targets.
Although the CDM did not
directly support CCS, another of the Kyoto Protocol’s flexible mechanisms called Joint
Implementation (JI) provided an alternate project-based mechanism to support CCS.
Much of the support for CCS has come from private industry, interested in the use of CO2
for enhanced oil recovery (EOR), in which CO2 is injected into crude oil reservoirs to
increase the amount of crude oil extracted, or by government funding sources wishing to
address GHG emissions as well as energy dependence on foreign governments.
Some of the current worldwide CCS projects are shown in Figure 1 (Carbon
Capture & Sequestration Technologies @ MIT, 2012). The majority of CCS projects are
located in developed countries and in areas where there are clear storage opportunities
(shown in Figure 2). Thus it seems that current carbon capture and storage technology
development may be determined both by the government’s will to fund development and
storage availability.
3
Figure 1. Worldwide CCS projects. Active and pilot CCS projects are shown in yellow
and blue, respectively; active storage only projects are shown in green (Carbon Capture
& Sequestration Technologies @ MIT, 2012). (Map data copyright 2012 MapLink, Tele
Atlas.)
Figure 2. Map of the world sedimentary basins with potential for carbon storage. (Figure
copyright, CO2CRC.)
4
United Kingdom
In October 2011, a £1 billion CCS power-station project located in Longannet,
Scotland was cancelled over a dispute over financing. Developers believed that the
project was underfunded and would require £1.5 billion from the British government to
maintain commercial viability (Gershman & Harvey, 2011). Despite this setback, the
British government has resolved to support use of CCS in coal-fired power plants and
appears to be prepared to relaunch its funding for CCS projects along with the U.S.
partner, Summit Power. This new project, located west of Edinburgh, Scotland, appears
to be another large-scale project, similar to the Longannet project, capturing carbon
emissions on more than 90% of production in a commercially scaled operation. The
captured CO2 will be transported by pipeline and sequestered in a nearby offshore
geologic area under the North Sea. Thus, although CCS development in the UK appears
to have suffered a temporary setback, the British government appears willing to continue
pursuit of CCS technologies.
Germany
On December 5, 2011 the Swedish company Vattenfall dropped plans to construct
a €1.5 billion CCS pilot project in Jaenschwalde, Germany, due to the rise in public
opposition to the project (Reuters, 2011). After initial approval of draft CCS legislation
by the German lower house of parliament, the legislation was rejected by the upper
house. Failure to resolve the concerns through mediation resulted in the withdrawal of
Vattenfall. A company statement suggested that without a clear legal framework in
place, the draft CCS law would be “insufficient for multi-billion investments in further
development of the technology.” One consequence of this development is that carbon
capture technology appears unlikely to be pursued much further in Germany in the near
term.
United States
In the United States, large-scale CCS projects are supported by a combination of
government funding and revenue generated by the use of CO2 in enhanced oil recovery
(EOR) operations—five out of six large scale CCS power plant projects (greater than 60
5
MW) in the US are partially supported with revenues from EOR and substantial
government support (Carbon Capture & Sequestration Technologies @ MIT, 2012). Out
of 10 projects proposed over the last 10 years, four CCS projects have been cancelled.
In two cases, the cancellation was a consequence of investors’ reluctance to make
substantial financial commitments before federal climate-change policies were clearly
established. In another case, the state government rejected funding after substantial
lobbying from environmental groups; in another, the cancellation occurred as a
consequence of project cost and schedule challenges in the midst of the economic
downturn.
Even active projects have had difficulties securing and sustaining funding and
political support. In 2003, FutureGen began as a promising public-private partnership
committed to producing the world’s first emissions-free coal-fueled power plant.
Substantial cost overruns eventually resulted in the U.S. Department of Energy
withdrawing support in 2008, although a revised plan was developed in 2010, and the
project was relaunched as FutureGen 2.0.
Because the large-scale power-generation projects are complex and require
substantial and secure governmental funding and legislative support, these projects are
difficult to support. There seems to be better support for smaller-scale research and
development of carbon-sequestration technologies. For example, the National Energy
Technology Laboratory (NETL) has received $70M in funding to investigate geologicsequestration site characteristics, and to support university research and development of
carbon sequestration.
NETL manages the Regional Carbon Sequestration Partnership
(RCSP), a partnership network investigating CCS approaches best suited to their
respective regions of the country.
India
Currently, India lacks policies or legislation to directly promote development of
CCS capability (Baker & McKenzie, Electric Power Research Institute, Schlumberger, &
WorleyParsons, 2009; Kapila, Chalmers, Haszeldine, & Leach, 2011), nor is it seen as a
immediate priority by the Indian government or industry stakeholders (Kapila et al.,
2011).
Without established GHG emissions targets, India may have little incentive to
6
pursue CCS technologies. Moreover, the historic exclusion of CCS support under the
Clean Development Mechanism of the Kyoto Protocol has discouraged external
investment. In 2008, India developed the National Action Plan on Climate Change in
recognition of the need to address the threat of climate change, as well as the need to
sustain economic growth.
The plan is largely focused on encouraging energy
conservation by promoting, for example, more efficient urban planning, use of energyefficient appliances, mandating limits on large energy-using industries, and enforcement
of automotive fuel-economy standards (Balachandra, Ravindranath, & Ravindranath,
2010). In the most recent draft of the plan (Prime Minister's Council on Climate Change,
2012), in comments related to CCS, it is noted that “feasible technologies for this have
not been developed and there are serious questions about the cost as well as the
permanence of the CO2 storage repositories.” Thus, it appears that, like Germany, India
remains skeptical about the long-term viability of carbon sequestration.
China
Large-scale CCS projects are currently in an early stage, although knowledge is
building from a variety of pilot projects (Best & Beck, 2011). China’s reliance on coal
and other fossil fuels for energy production will require some form of CCS (Morse, Rai,
& He, 2010), especially if China agrees to limit emissions in the future.
Binding
emissions targets are expected to be established in China by 2020 (Stanway, 2011). To
that end, China recently ordered seven provinces and cities to establish GHG emissions
caps and plans to establish an internal carbon market (Stanway, 2012).
Counter to this broad trend is the difficulty posed by the Chinese government’s
control over internal electrical prices. In 2008, these controls made it difficult to absorb
fluctuating prices in the coal markets (Morse et al., 2010); this, in turn, suggests that the
government may not be prepared to invest in CCS without some form of external support.
And, since CO2 capture reduces power-generation efficiency (in large power plants) by
20 to 30%, there may be a further disincentive to invest in CCS technologies.
7
Recent developments
Developments at the United Nations Framework Convention on Climate Change
(UNFCCC) in Durban (2012a) have recently allowed CCS projects under the Clean
Development Mechanism (CDM). The agreement includes provisions for selection of
storage sites, addressing remediation of CO2 seepage, measures to address
nonpermanence, and long-term liability. While this move was heralded as a means to
unlock the application of CDM benefits to drive CCS development, the European Union
(EU) has resolved to purchase CERs exclusively from CDM projects located in Least
Developed Countries (LDC) (Nell & Guilder, 2012). One consequence of this policy
would be for the EU, as the largest buyer of CERs in the international market, to exclude
China, India, Ghana, Qatar, the United Arab Emirates, and South Africa from CDM.
These are the countries that are most likely to increase their use of fossil fuels to feed
their increasing need for power (Nell & Guilder, 2011).
Conclusion
While there have been encouraging signs that CCS is gaining acceptance as a
means to reduce carbon emissions, the overall outlook looks somewhat mixed. Attempts
to establish large-scale integrated CCS projects have faltered because of cost overruns
and government withdrawal of support. In the UK, this was especially apparent in the
cancellation of the Longannet project. In Germany, heightened environmental concerns
and lack of adequate legislative protection may have redirected focus toward alternatives
to fossil-fuel use. In the United States, while there seems to be minor environmental
concern about the injection of CO2 into geologic formations for enhanced oil recovery,
the cost of collection and sequestration may have weakened political resolve to address
issues of climate change. Unless the U.S. enters the emissions trading market, the
financial incentives to push development may be missing. India appears to be focused on
energy conservation and appears unwilling to consider CCS as anything more than a
potentially risky technology. China appears willing to consider CCS, but it remains to be
seen how much loss in power generation efficiency it may be willing to absorb.
8
This review of global CCS was intended to establish a picture of what the future
geographic distribution of CO2 sequestration may look like, especially in countries where
motor-vehicle use is high or rapidly expanding. If collection of CO2 emissions from
vehicles is to become commonplace, long-term storage outlets for CO2 will be needed. At
present, it seems that CCS technologies are still at too early a stage of development to
make any clear forecasts.
9
Carbon-Collection Processes in Vehicles
Power generation is responsible for about 39% of CO2 emissions in the United
States (United States Environmental Protection Agency, 2011b). Thus, it is no surprise
that carbon capture and sequestration technologies have largely focused on the powergeneration industry where carbon dioxide is produced in large quantities at a single
stationary site.
A recent report explores the application of carbon capture to small
distributed power sources where carbon dioxide might be captured directly from the
exhaust stream of, for example, an automobile (Damm & Fedorov, 2008b). If such a
system is indeed feasible, there are several questions regarding consumer acceptance that
might arise. How will consumers view the choice between continued reliance on fossilfuel combustion and the growing number of alternative power sources that are considered
both cleaner with respect to emissions, and sustainable with respect to renewability?
How will perceived need for travel range, flexibility, and operating convenience weigh
against the demand for lower carbon emissions? How much CO2 emissions reduction
would offset a perceived contribution to global warming? Would tangible accumulation
of carbon dioxide heighten general awareness of the hidden costs of combustion? How
would the added task of offloading collected carbon dioxide affect the consumer’s
perception of convenience?
Why is fossil fuel combustion an attractive option?
Combustion of gasoline fuel in transportation has many advantages over
alternative sources of energy for the average consumer. Gasoline has relatively high
energy density (about 32 to 35 MJ/L) compared with ethanol (~21 to 24 MJ/L),
compressed natural gas (CNG, 9 MJ/L compressed at 250 bar), propane (25 MJ/L
compressed at 12 bar), electricity, or hydrogen (5.6 MJ/L compressed at 700 bar)
(Greene, Baker, & Plotkin, 2011; Greene & Schafer, 2003; Oak Ridge National
Laboratory, 2012). An average gasoline-powered vehicle can be driven more than 300
miles after a single fueling. By comparison, the travel range of the current generation of
consumer electric vehicles is less than 100 miles between recharges. Range for electric
vehicles is also reduced in cold operating conditions, and recharging may take between 4
10
and 8 hours, compared with the few minutes it takes to refuel a gasoline vehicle. From
the consumer’s perspective, electric vehicles require “refueling” more frequently than
gasoline-powered vehicles, and the time spent recharging the vehicle effectively renders
the vehicle unavailable.
Other low-emissions fuels that are maintained in a gaseous state, like compressed
natural gas (CNG) or hydrogen, are more difficult to transport than gasoline. Some are
gaseous at ambient temperatures and must be compressed and liquefied (e.g., hydrogen,
LPG, CNG), requiring a more complex delivery infrastructure than gasoline. Use of fuels
held in pressurized tanks may also be perceived as a danger should the vehicle become
involved in a collision.
Finally, the cost of alternatively powered vehicles remains much higher than
gasoline-powered vehicles. For example, the suggested retail price of a 2012 Chevrolet
Volt is about $40K, while the 2012 Chevrolet Cruze, a comparable gasoline-powered
vehicle, starts at $16,800; the average price difference between a hybrid vehicle and a
gasoline-powered sibling vehicle ranges between $4,000 and $8,000—the difference
between a 2012 Toyota Camry and Camry Hybrid is about $4000, the difference between
a 2012 Ford Fusion and Fusion Hybrid is about $8000.
Comparison of energy sources
Gasoline and Diesel. Gasoline combustion is relatively inexpensive and versatile
compared with other energy sources used in transportation. By volume, the energy
density of gasoline is relatively high—about 32 to 35 megajoules per liter (MJ/L)—
providing significant portability for a large amount of energy (Edwards, Larivé, & Beziat,
2011). Gasoline is a liquid, allowing precise control of the combustion process (unlike,
for example, solid fuels like coal).
Gasoline can be ignited at very low ambient
temperatures (-45 deg F), but has a high spontaneous-ignition temperature, making it
suitable for use in vehicles subject to wide variation in operating temperature.
Gasoline combustion generates about 73 grams CO2 emissions per megajoule (g
CO2e/MJ), excluding emissions during production.
11
By comparison, combustion of
propane gas produces 65 g CO2e/MJ; compressed natural gas (CNG), 56g CO2e/MJ; and
ethanol 71g CO2e/MJ. Combustion of hydrogen produces no carbon emissions.
Gasoline, like all fossil fuels, is a nonrenewable resource—oil depletion estimates
vary widely, but many suggest peak production will be reached in the very near term
(Kjärstad & Johnsson, 2009; Miller, 2011; Sorrell, Speirs, Bentley, Brandt, & Miller,
2010). Finally, the efficiency of gasoline engines is relatively low. Estimates suggest
that conventional gasoline engines use only about 14 to 26% of the fuel-energy content to
propel the vehicle or power accessories (United States Department of Energy, 2012b).
Engine efficiency plays a significant role in determining the ultimate emissions profile of
a vehicle. For example, although combustion of diesel fuel produces similar carbon
emissions to gasoline (i.e., 72.6 gCO2e/MJ), diesel engine efficiency is higher (about 2030%). The resulting carbon dioxide emissions produced by a diesel engine per mile of
travel is typically lower than that produced by a gasoline engine, although diesel engine
emissions of particulate matter (black carbon) may be even more damaging to the
atmosphere (Quaas, 2011). In vehicles powered by electric motors, efficiency is about
75%.
Compressed Natural Gas (CNG—methane). Compressed natural gas has been a
popular alternative to gasoline, particularly in fleet operations. CNG produces lower
carbon emissions than gasoline (56.24 g CO2e/MJ), as well as lower-sulfur oxides,
nitrogen oxides, and particulate matter. Like gasoline, CNG has a low flashpoint (-300
deg F) and a relatively high autoignition temperature (842 deg F), making it a suitable
fuel across a wide range of temperatures. The cost of CNG is about half that of gasoline.
Disadvantages include the relatively low energy density of CNG, about 9 MJ/L.
This means that in order to carry a comparable amount of energy as provided by gasoline,
more of the vehicle’s storage space is required for fuel, reducing the available space for
other cargo. Although natural gas is widely used in household cooking and heating, in
vehicle applications, it is compressed and held in high-pressure storage tanks (3500 psi);
refueling requires special refueling connections to manage refueling under high pressure.
This limits a consumer’s refueling options. In half of the states in the US, there are fewer
than 10 public refueling stations per state (United States Department of Energy, 2012a).
12
Natural gas (i.e., methane) is also a more damaging GHG contributor to global
warming than carbon dioxide. Any leakage in a CNG system would produce more
damaging environmental effects than CO2 emissions—the UNFCCC estimates methane
to have 21 times the global warming potential of CO2 over a 100-year time horizon
(United Nations Framework Convention on Climate Change, 2012b).
Other Gases: LPG is composed principally of propane and butane, and is
popularly used where a natural-gas infrastructure or pipeline is unavailable. The energy
density of LPG is 25 MJ/L: much higher than CNG, but significantly lower than gasoline.
CO2 emissions from LPG combustion are 65 g CO2e/MJ, which is higher than CNG, but
lower than gasoline.
Direct combustion of hydrogen gas has been used in limited applications since the
earliest internal-combustion-engine designs. Hydrogen is also used to power fuel cells, in
which hydrogen gas is used to generate electrical power through an electrochemical
process. In both cases, the byproduct of the fuel consumption is water. While the lowemissions characteristic of hydrogen is attractive, use of hydrogen for combustion may be
impractical. The low efficiency of internal-combustion engines compared with electric
engines (14% versus 75%), coupled with the small volumetric energy density of
hydrogen—at 700 bar, the energy density of hydrogen is 5.6 MJ/L—suggests that an
internal-combustion engine powered exclusively by hydrogen may have an unacceptably
limited range.
A key reason for hydrogen’s popularity is that the supply of hydrogen is
perceived as limitless, and its combustion byproduct, water, is harmless. The processes
used to obtain hydrogen, however, can involve undesirable secondary costs.
For
example, hydrogen is commonly produced from natural gas by a process called steam
reforming. An undesirable byproduct of this process is CO2, as well as the emissions
produced to generate the steam used in the reforming process.
In a “well-to-wheels” (or life-cycle) analysis by the U. S. Department of Energy
(United States Department of Energy, 2005), fuel-cell electric vehicles were estimated to
produce 45% and 24% less CO2 emissions per mile than conventional ICE vehicles and
hybrid-electric vehicles, respectively. This analysis factored in all emissions generated
13
during production of the fuels.
Such an analysis is reasonable, provided that fuel-
production processes are somewhat standard, although for some fuels, there may be
significant differences in emissions generated during the production process. Accounting
for emissions in this way may also be too subtle from a consumer’s perspective. For
example, electric vehicles (EVs) are widely considered environmentally friendly without
regard to the actual manner in which the stored electrical power was generated (Anair &
Mahmassani, 2012).
Another disadvantage of hydrogen fuel is that fuel-cell technology is more
sensitive to temperature extremes than gasoline-powered internal-combustion engines.
For example, the operating temperature of a Polymer Electrolyte Membrane (PEM) fuel
cell ranges between 50-100 deg C. Because fuel cells produce water as a byproduct of an
electrochemical process, freezing temperatures pose some difficulties for fuel cells. In
early designs, fuel-cell vehicles were limited to operating in above-freezing temperatures
because, in subfreezing temperatures, formation of ice on the PEM would damage the
membrane, and ultimately shorten the lifetime of the fuel cell.
Biofuels. Unlike most fuels, biofuels directly invite consideration about the fuel’s
origin—i.e., carbon from the atmosphere. To the consumer, many parts of this process are
largely unseen. Current concerns about vehicle emissions, highlighted by motor-vehicleemissions tests, are focused on the toxic byproducts of combustion—unburned fuel,
nitrogen oxides and carbon monoxide—at the end-use of the fuel. A consumer might
therefore judge the entire emissions impact of his or her vehicle based on end-use of the
fuel. Although consumer awareness might be increased if efforts are made to publicize
how the electrical power used to recharge the vehicle is generated, consumers are
ordinarily unaware of the details of power generation. Similarly, consumers are also
likely to be poorly acquainted with the generation of other alternative fuels.
Biofuels is one exception. The perceived virtue of biofuels is that they only burn
carbon that was removed from the atmosphere; biofuels are carbon neutral. Combustion
of this fuel simply returns it back into the atmosphere, resulting in no net increase in
carbon dioxide. Thus, to see the emissions benefit in biofuels, one must consider more
than what happens at combustion. It requires the knowledge that the fuel’s carbon
14
content was removed from the atmosphere by biological processes that transformed
carbon dioxide in the atmosphere into the biomass from which the fuel is derived.
Recently, the carbon neutrality of biofuels has been challenged and defended in a
variety of life-cycle analyses (e.g., DeCicco, 2012; Johnson, 2009; Searchinger et al.,
2009). Whether biofuels are indeed carbon neutral seems to depend on numerous factors,
including changes in land use, depletion of forest stocks, the energy consumed during
fuel production, and whether any portion of the biomass is converted to biochar (i.e., the
charcoal byproduct of pyrolysis of plant material) and returned to the soil (Mathews,
2008).
In any case, it is unlikely that consumer opinion will be driven by the
complexities of such life-cycle analyses. Most likely, biofuels will be attractive because
of their similarity to fossil fuels in how they are distributed and consumed in vehicles, the
size and variety of vehicle selection supporting biofuels, beliefs about the use biofuels
and energy independence, and the understanding that biofuels represent a renewable
energy resource.
Biofuels include all fuels derived from the biological action of carbon fixation.
There are two broad classes of fuels—bioalcohols, produced by fermentation; and
biodiesel, made from vegetable oil. The most common bioalcohol fuel is ethanol. The
energy density of ethanol is lower than gasoline (~21 to 24 MJ/L). Thus, a vehicle cannot
travel as far on one tank of ethanol as it can on one tank of gasoline. To moderate this
disadvantage, ethanol is often mixed with gasoline in varying proportions, designated by
a numeric suffix (for example, E5 is 5% ethanol, E10 is 10% ethanol, and so on for E15,
E25, E85 and E100). The level of carbon emissions from ethanol combustion is
comparable to gasoline—71.6 g CO2e/MJ. However, as was pointed out above, carbon
emitted during combustion was previously removed from the atmosphere during carbon
fixation.
Biodiesel fuels have an energy density comparable to fossil fuel diesel—33 MJ/L.
Like ethanol, biodiesel fuels are blended with conventional diesel fuels to produce
various B grades of biodiesel. For example B2 is 2% biodiesel, B5 is 5% biodiesel, and
so on for B20, and B100. Use of blends greater than B5 in diesel engines would
generally violate a manufacturer’s warranty, unless the vehicle explicitly supports them.
15
Biodiesel CO2 emissions during combustion are actually higher than for fossil diesel—
about 75 g/MJ for biodiesel generated by rapeseed oil, compared with 72.6 for fossil
diesel.
Estimates of biofuel production in the United States suggest that it may take about
50 M acres to produce roughly half of the current US consumption of gasoline, and the
production of ethanol, for example, consumes almost as much fossil-fuel energy as it
replaces (Chu, 2008). Biofuels also pose the ethical dilemma of the tradeoff of food for
fuel, although second generation biofuels produced from the lignocellulose in nonfood
plant material—e.g., wood pulp, switchgrass, and agricultural waste—could mitigate this
issue, provided the land used to cultivate this source does not directly compete with food
cultivation. Finally, regardless of the crop, biomass yields may not be sufficient to meet
projected levels of transportation consumption (Walker, 2009).
From the consumer’s viewpoint, the similarity of biofuels to fossil fuels with
respect to distribution network, operational factors, and energy density (depending on
mixture and fuel type), makes the choice to switch to fuels blended with biofuels unlikely
to present drivers with any specific hardships. Moreover the variety of flex-fuel vehicles
(FFV), although smaller than gasoline-powered vehicles, is greater than CNG vehicles,
electric, or hybrid electric vehicles. And, because these vehicles can also burn gasoline,
there is more flexibility in locating fueling stations, despite the limited distribution of E85
fueling stations (i.e., fewer than 10 in 19 of the U.S. states; United States Department of
Energy, 2012a).
Any carbon-capture method developed for gasoline combustion would also be
adaptable for use with biofuels. The net benefit of a biofuels coupled with carbon capture
could conceivably be carbon negative—that is, more carbon would potentially be
removed from the atmosphere than is emitted during combustion.
Electric Vehicles. Key advantages of electrically powered vehicles are that they
are emissions free, they use electrical motors that are more efficient than internalcombustion engines, and they can be recharged using household electrical service.
Secondary advantages include the potential use of vehicle-based electrical storage as a
resource to address periods of peak electrical demand on the electrical grid.
16
Disadvantages include the relatively low energy density of most current battery
technologies (Fischer, Werber, & Schwartz, 2009). One hypothetical estimate of an
advanced battery module suggests an energy density of about 1-2 MJ/L (Global Climate
& Energy Project, 2006). This is significantly less than the energy density of gasoline
and, despite the energy efficiency of electric motors, the range of a vehicle powered by a
battery alone remains comparatively low. As discussed above, there are also potentially
hidden emissions that depend on how the power stored in the vehicle’s battery was
generated. The vehicle’s real carbon impact could be much higher than is immediately
apparent to a consumer.
Consumer Relevance. From a consumer’s perspective, experience with the use of
fossil fuels to power vehicles establishes a benchmark against which alternatively
powered vehicles are likely to be evaluated. The impetus to consider ways to mitigate
carbon dioxide emissions would most likely be driven by a heightened awareness of
carbon dioxide’s contribution to global warming and by an understanding about the
quantities typically generated during combustion. While the link between climate change
and anthropogenic greenhouse gases is generally accepted in Europe, it has been
contested in the popular media in the United States. The extent to which a consumer
believes that there is an obligation to reduce one’s individual carbon footprint will drive
the decision to accept different alternative fuel solutions. With this in mind, the switch to
use of biofuels may be the easiest option to adopt, provided that biofuels become more
widely available. The direct cost to a consumer would be about 10% fewer miles per
gallon (with E85). Such a reduction in fuel economy might easily go unnoticed by
drivers amid the other sources that contribute to mileage variability—for example, cargo
weight, speed, use of air conditioning, etc. (Sivak & Schoettle, 2011).
And, even if
biofuels are unavailable, a vehicle that is fueled by E85 can also be fueled by gasoline.
Vehicles powered by hydrogen or CNG are generally designed to burn this fuel
exclusively, although some hybrid designs permit use of gasoline as a backup fuel (e.g.,
the BMW Hydrogen 7). In most cases, these vehicles are used in vehicle fleets in which
each vehicle daily departs and returns to a central depot. While this use model fits shortdistance delivery services, it may not reflect the desired operational use of an average
consumer of a passenger vehicle.
17
Gasoline is also used as a backup fuel to extend the range in most plug-in hybridelectric vehicle (PHEV) designs. The Chevy Volt is a series hybrid vehicle that uses a
gasoline engine to drive an electric generator to recharge the battery that powers the
electric motor; PHEV versions of the Toyota Prius are parallel hybrids and use either a
gasoline or an electric motor to propel the vehicle. The only commercially available fully
electric vehicles currently available on the U.S. consumer market are the Nissan Leaf, the
Mitsubishi MiEV, and the Smart Fortwo.
Plausible in-vehicle carbon-capture mechanisms
Carbon-capture techniques are most highly developed in the power-generation
industry. There, carbon capture may occur at three different points in the combustion
cycle (shown in Figure 3):
1. Before combustion (pre-combustion)—where a fossil fuel is partially oxidized
to produce syngas (CO and H2O) and then shifted to produce CO2 and H2; the
CO2 is then selectively removed leaving only the hydrogen gas to support
combustion.
This method is most highly developed in commercial
applications (Global CCS Institute, 2011).
2. After combustion (post-combustion)—where a mixture of carbon dioxide,
oxygen, and nitrogen compounds is produced, requiring a post-combustion
separation process. Post-combustion-capture methods have an advantage that
they may be more easily retrofitted to existing combustion systems.
3. After removal of all but the oxygen from the combustion chamber so that the
principal combustion byproduct is CO2 (oxyfuels)—this simplifies postcombustion processing since the resulting byproduct is relatively pure carbon
dioxide. The process eliminates the necessity of separating the CO2 from
other gases in the exhaust stream.
Besides these carbon-capture mechanisms, which are based on capture methods
used in power generation, other methods have been proposed which involve use of
gasoline along with light metal hydrides and carbides to trap CO2 (Seifritz, 1993), or to
18
separate hydrogen directly from gasoline, using only the hydrogen for combustion
(Damm & Fedorov, 2008a).
If a carbon-capture process was to be implemented in automobiles, it would most
likely first employ post-combustion capture, since this could be appended to the
downstream management of exhaust gases without directly affecting the inputs to the
internal combustion engine.
Figure 3. Carbon capture and storage. Illustrates post-combustion, pre-combustion, and
oxyfuel processing (Cooperative Research Centre for Greenhouse Gas Technologies
(CO2CRC), 2012).
Post-combustion removal of carbon dioxide from the exhaust gas stream can be
accomplished three basic ways:
1. Absorption. In this method, exhaust gases are first passed through a liquid
medium into which the carbon dioxide selectively dissolves. A second step is
required to remove the carbon dioxide from the solution. This is generally
done by heating the solution to remove the carbon dioxide for capture and
storage (see Figure 4). This method is commonly used for carbon capture on
a small scale and is being adapted for use in large-scale coal-burning
electrical-power operations (Global CCS Institute, 2011).
19
Figure 4. Carbon dioxide removal by absorption (Cooperative Research Centre for
Greenhouse Gas Technologies (CO2CRC), 2012).
2. Membrane separation.
In this process, CO2 is separated from the other
exhaust gases using a semipermeable membrane that allows CO2 to pass
through more easily than other gases in the exhaust stream. The separated
CO2 is then captured for later storage. This process requires high pressure to
drive the separation.
Figure 5. Carbon dioxide separation by membrane selectivity (Cooperative Research
Centre for Greenhouse Gas Technologies (CO2CRC), 2012).
20
3. Adsorption. In this process, CO2 first selectively adheres to the surface of a
material without forming a chemical bond while other gases pass through.
This is done under either increased pressure or decreased temperature. In a
second phase, the CO2 is separated by reducing the pressure and/or increasing
the temperature, allowing the CO2 to be drawn off.
Figure 6. Carbon dioxide separation by adsorption (Cooperative Research Centre for
Greenhouse Gas Technologies (CO2CRC), 2012).
Transport to long-term sequestration areas
Because suitable areas for CO2 sequestration are not available everywhere, CO2
may need to be transported over significant distances for proper long-term storage. The
most efficient means of transporting large volumes of CO2 is by pipeline to a
sequestration reservoir equipped with the necessary long-term monitoring technologies
required to detect leakage. In a report to the U.S. Congress, the Congressional Research
Service (Parformak & Folger, 2008) suggests that there is growing recognition in
Congress that a substantial interstate network of CO2 pipelines will be required in the
future to reduce carbon emissions produced during electrical power generation.
However, divergent views on pipeline requirements and cost estimates are likely to
complicate the federal government’s role.
21
The cost of CO2 transportation is directly related to pipeline length, and this cost
will contribute to regional differences in electricity prices. There is currently no federal
authority governing CO2 pipeline siting—as CO2 pipelines increase in length they will
cross more state jurisdictions, and the regulatory mechanisms governing licensing and
approval will become complicated. Moreover, the involvement of many jurisdictions will
likely involve more public scrutiny and possible opposition.
While CO2 transportation costs might be reduced by situating power plants near
suitable carbon-sequestration locations, power-generation costs are generally dominated
by distance from electricity consumers. If it comes down to a tradeoff between long
pipelines or long power lines, longer pipelines will be the preferred choice (Parformak &
Folger, 2008). This might be good news for sequestration of the comparatively small
quantity of CO2 collected from vehicles relative to that collected from power plants—
longer pipelines create more opportunity to tap into growing sequestration infrastructure.
If carbon capture is to succeed at the vehicle level, it will require some infrastructure to
collect and transport CO2 to an appropriate storage site.
It is unclear what long-term
government policies will be required to support the construction and sharing of such
pipelines.
22
Considerations about the Operational Costs of Carbon Capture
Amount of CO2 recovered
One gallon of gasoline weighs about 2.7 kg; combustion of one gallon of gasoline
produces 8.9 kg of CO2. If all CO2 is captured after combustion, not only will the
vehicle’s weight increase, but the volume required for CO2 storage will exceed the
volume displaced by gasoline.
This issue can be addressed in a variety of ways,
including requiring more frequent offloads of collected CO2, allocation of more storage
volume for CO2, or reduction of the amount of CO2 captured during the combustion of
one tank of gasoline.
As an initial approximation, we might assume that storage-volume allocation for
CO2 is the same as for gasoline storage for illustration. However, it is unclear whether
this is practical, or whether some method might be developed to reclaim the space
vacated by the gasoline. Nevertheless, if it is assumed that the stored CO2 can be
compressed and stored in a liquid state (at about 73 bar), the resulting volume would be
about three times the space required for gasoline. If the same volume is used for fuel and
CO2, this would require the vehicle operator to offload CO2 three times per refuel with
gasoline.
The second alternative, allocation of additional storage for the CO2, would require
the consumer to sacrifice vehicle storage space. To capture all of the CO2, a volume of at
least three times the size of the fuel tank might be needed to manage the storage demand.
The third option, reduction in the amount of CO2 emissions captured, reduces the
value of the environmental contribution of the carbon-capture process. For example, if
only 33% of carbon emissions are captured, the resulting accumulated CO2 might occupy
the same volume as a tank of gasoline. While consumers seem to generally value lowemissions vehicles, this may be based on a broad heuristic sense that it is generally good
to curb consumption of an item known to be in limited supply. Moreover, it can save
money on fuel as well. It is unlikely, however, that consumers are as aware of the
amount of CO2 produced during vehicle operation. For most US consumers, awareness
of vehicle emissions might stem from their experience with various jurisdictions’
23
departments of motor vehicles (DMVs) vehicle-emissions-testing protocols. Emissions
testing evaluates the amount of toxic emissions—carbon monoxide, unspent fuel, and
nitrogen oxides—that exit the tailpipe. To pass an emissions test could easily suggest to
a consumer that his vehicle has met an environmental benchmark and is certifiably
“clean.”
For example, Georgia’s emissions testing is administered through an
organization called Georgia’s Clean Air Force; most DMVs’ emissions testing explicitly
links vehicle emissions to air pollution. Thus, immediate concerns about CO2 emissions
may be small among consumers whose familiarity with the gas stems from its use in
beverage carbonation, production of dry ice, and paintball propulsion.
Parasitic load of the in-vehicle capture process
Each of the CO2 separation processes described earlier requires varying amounts
of energy to accomplish the CO2 separation and to store the CO2 under pressure. Some
separation processes require changes in temperature and pressure; storage of the extracted
CO2 would need to be held in a tank, under compression. Depending on the amount and
area reserved for storage, this would require more or less compression, which would
require additional energy. The additional energy used to support separation and storage
is called the “parasitic load” and results in some reduction of operating efficiency. For
example, in electrical power generation, estimates of the loss in output (i.e., energy
penalty) with carbon-capture range between 15% and 35% (Page, Williamson, & Mason,
2009). Parasitic energy also depends on the percent of the carbon captured. It is unlikely
that losses in a vehicle-based capture process would be quite as large as in power
generation, especially if some of the energy loss due to inefficiencies in the combustion
engine (e.g., heat) can be redirected toward the separation-and-capture processes. For
consumers, parasitic energy cost means that a fraction of fuel energy will be consumed to
support the separation and storage of CO2. The acceptability of this cost cannot be
understood unless a cost in fuel economy can also be determined so that a consumer can
weigh this against the desire to reduce CO2 emissions.
24
Discharge procedures for carbon capture
Assuming that CO2 is held in on-board storage within a vehicle, procedures to
offload CO2 must also be considered.
A logical approach would be to establish a
discharge process that can be performed in tandem with the refueling. This would be
akin to the recycling of the used engine oil during an oil change, or the exchange of a
spent propane tank when a full tank is purchased. Thus, it would be optimal to discharge
accumulated CO2 at the same service station used to refuel. An efficient procedure
would also allow discharge operations to occur at the same time as refueling, so that the
overall duration of the operation may be no different than average refueling times. Such
a tandem refuel/discharge operation would be best simplified if only one connection was
required to accomplish both tasks. For example, a dual hose might be designed to send
fuel on one line and remove CO2 on the other.
It is also important that refueling operations not be restricted if the on-board CO2
storage is full. It is likely that refueling locations will significantly outnumber discharge
locations.
Coupling fueling/discharge operations so that CO2 discharge would be
required before refueling would be too restrictive for consumers and perhaps deter
adoption this technology. This issue suggests that reclaiming storage space vacated by
fuel consumption for CO2 storage could initially place a burden on consumers since
refueling would be obstructed until the CO2 could be discharged. That is, initially limited
opportunities to discharge CO2 should not result in a disabled vehicle, if CO2 storage
reaches capacity, nor should it restrict refueling operations. On the other hand, if there
are no restrictions on refueling and vehicle operation with CO2 storage at full capacity,
the consumer incentive to collect CO2 may be weak. That is, if collection and discharge
costs additional time and money, consumers may need more direct encouragement to
continue carbon collection.
Depending on the consumer, encouragement may be
provided by monetary reward for CO2 discharge, or the ability to directly monitor the
cumulative amount of CO2 emissions collected.
25
Location of carbon-collection facilities
Planning for the introduction of a limited distribution of carbon-collection
facilities is similar to planning the placement of refueling sites in an alternative-fuel
network. Just as opportunities to use alternative fuels may be limited during early stages
of introduction, resources to offload collected CO2 may be similarly limited. Consumers
would then need to plan to discharge more consciously than if discharge facilities were
more widely available. In an analysis of the diesel refueling behavior of drivers, Sperling
and Kitamura (1986) found that predictability of fuel-station location compensates for
reduced fuel availability. In 56% of the cases, diesel-vehicle operators preferred fuel
outlets proximate to their home, work, or school, while only 29% of gasoline-car drivers
preferred outlets based on these criteria. The limited number of discharge stations will
also obligate early adopters of vehicles equipped with CO2 capture capability to devote
more attention to consideration of when and how to offload CO2. This will be true,
provided that they can sustain the motivation to reduce carbon emissions. However,
unlike the situation where fuel availability is limited, the consequence of failing to plan
the discharge of CO2 should not necessarily result in a disabled vehicle. A full CO2 store
may simply mean that carbon-emissions capture is temporarily disabled. With such a
small penalty, it is unclear whether drivers will be well motivated to plan for CO2
discharging. It is conceivable that without additional incentives, consumer resolve to
collect CO2 emissions may not be high.
More detailed studies of the spatial distribution of driver refueling patterns seem
to support these observations. For example, drivers tend to refuel in familiar places—
close to home or workplace—and at the beginning or end of their trips (Kitamura &
Sperling, 1987). In studies of the spatial distribution of alternative-refueling decisions,
demand for refueling was related to distance traveled, with the exception of specific
refueling trips to a central business area in a densely populated area (Nicholas, 2010;
Nicholas & Ogden, 2006); refueling decisions were also observed to occur most
frequently between home and the freeway (Nicholas, 2010). One upshot of this analysis
is that stations located along a freeway may best serve initial customer demand.
26
Additional maintenance costs
Most vehicle operators are required to perform regular maintenance on their
vehicles to ensure that the vehicle performance remains optimal. Routine maintenance
items include changing out motor oil, the oil, air, and fuel filters, coolant, tire rotation,
belts, etc. Automobile manufacturers establish regular maintenance intervals, typically
between 3,000 and 7,500 miles.
It is important that the maintenance of in-vehicle
carbon-capture technologies conform to the same maintenance pattern for other vehicle
components. In addition, the costs of components related to carbon capture should not
exceed the customary range of other vehicle-maintenance items.
27
Consumer Purchase Motivations
Forecasting consumer adoption of an innovative transportation technology is a
complex undertaking and involves several marketplace mechanisms. In an agent-based
model (ABM) used to characterize the diffusion of alternative-fuel vehicles (AFV),
Zhang, Gensler, and Garcia (2011) have modeled three key participants in this process.
First, there are manufacturers, who play a role in bringing innovative products to the
marketplace. This creates a technology push of the innovation onto consumers. Second,
the consumer must desire the innovation so that some market pull is generated to
encourage innovation.
This second factor is influenced by a consumer’s direct
knowledge of the product and by reliance on word-of-mouth from other consumers or
trusted sources. Third, the authors suggest that, especially with respect to eco-innovation
in transportation, there is a significant role played by regulatory intervention that may
generate some pull on the consumer side (e.g., tax deductions for low-emissions vehicle
purchases) or push on the manufacturer side (e.g., Corporate Average Fuel Economy—
CAFE regulations). While many low-emissions vehicle technologies are beginning to be
seen in the marketplace, there remains insufficient market demand to encourage
manufacturers to broaden their offerings to the level seen with gasoline-fueled vehicles.
Some consider that, while the broad opinions about alternative-fuel-vehicle technologies
are generally positive, significant adoption will depend on how these vehicles compare
across several dimensions with respect to conventional vehicles (Shepherd, Bonsall, &
Harrison, 2012).
Other consumer research suggests that a significant part of the motivation for the
purchase of a low-emissions vehicle is related to perceived financial benefit: low
emissions mean low fuel consumption; low fuel consumption means low fuel cost (Ozaki
& Sevastyanova, 2011). Indeed, models of consumer motives to adopt a low-emissions
vehicle seem to focus on the consumer’s desire to offset the higher cost of a hybrid or
electric vehicle with direct financial benefit (Caulfield, Farrell, & McMahon, 2010;
Eggers & Eggers, 2011; Ozaki & Sevastyanova, 2011; Shepherd et al., 2012). This
suggests that lowered carbon emissions may not alone present sufficient consumer
incentive unless some financial benefit can be directly coupled to the collection of CO2.
28
In the current marketplace, because low emissions are linked to higher fuel efficiency,
consumers expect low-emissions vehicles to result in lower fuel costs. If carbon-capture
technology is applied to vehicles, however, this relationship between fuel consumption
and emissions is altered in a way that consumers may not readily understand. It may thus
be possible to make a low-emissions vehicle that has the equivalent emissions of a hybrid
vehicle, but which has the fuel economy of a heavier vehicle. Whenever a driver of a
low-emissions vehicle refuels, the fuel-pump tally provides tangible and reinforcing
information that there are benefits in driving a low-emissions vehicle. Unless a similarly
reinforcing benefit can be made tangible when carbon dioxide is discharged from a
vehicle equipped with carbon-collection technology, drivers will have little to reinforce
their decision to adopt this technology. This suggests that carbon-collection incentives
may be needed to support this technology. Without a widely adopted carbon-emissions
policy, few incentives are likely to develop to directly support carbon collection.
One approach to creating such incentives would be to attach a “deposit” or
surcharge on the price of a gallon of gasoline to cover the resulting CO2 emissions
generated during combustion, much like a deposit is charged on the cost of a beverage
bottle to encourage return of the bottle for recycling. When the collected CO2 is returned,
the surcharge is then refunded back to the consumer. Similar surcharges have been
considered to address the increasing amount of cell phone and e-waste refuse (Kahhat,
Junbeum, Ming, Allenby, & Williams, 2008; Silveira & Chang, 2010).
29
Conclusions
This survey of the feasibility of introducing CCS into light vehicles initially
reviewed the level of international support for CCS with the view that unless countries
establish policies and infrastructure to support CCS, there may be little point in collecting
CO2. In general, it appears the CCS is still a developing technology; the expense and
uncertainties of large-scale projects make it difficult to obtain financial support without
governmental participation. This has been a problem in the US and the UK. Uncertainty
in legislative protection has deterred private investment, particularly in Germany. India
does not appear to be considering use of CCS and appears, instead, focused on
improvements in fuel efficiency; China, a significant consumer of coal, appears interested
in adopting CCS in coal-powered generation of electricity, but there is some uncertainty
about their willingness to absorb losses in power-generation efficiency.
Fossil fuels continue to be a versatile means of energy storage, especially
compared with many low-emissions alternatives.
Positive attributes associated with
gasoline-powered vehicles—e.g., travel range, performance across temperature ranges,
fuel availability, and cost—continue to make gasoline attractive relative to many
alternative fuels. This is noted because, apart from reduced fuel consumption, CCS
technology is key to reducing CO2 emissions produced by the use of fossil fuels in
transportation. CCS technology can also be applied to biofuels, potentially creating a
carbon-negative outcome.
Among the capture mechanisms reviewed, post-combustion technologies were
given focus because these mechanisms are most likely to be readily adaptable to operate
with existing internal-combustion engines. Three separation processes were described:
absorption, membrane separation, and adsorption.
Considerations about operational costs from the point of view of the consumer
were discussed, including storage management of captured CO2, additional energy costs
to support separation and storage, discharge procedures, and additional maintenance
costs. In light of these considerations, models of consumer inclination to adopt new
technologies were reviewed.
In many models, consumer motivation is driven by
30
perceived financial benefit, suggesting that incentives beyond reduced emissions may be
required to motivate consumers.
31
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